The name of your macOS user account and the name of your home folder must both be the same. Changing these names does not change or reset the password of your user account.

The IP address or name of the server you most recently connected to is selected by default. In the User name text box, type the user name. If Mobile VPN with SSL on the Firebox is configured to use multiple authentication methods, specify the authentication server or domain name before the user name. For example, ad1example.comjsmith.

Because doing this incorrectly could damage your account and prevent you from logging in, you should back up your important data before proceeding.

• Sep 30, 2009  This answer is very helpful. I was unable to activate MatLab on my borrowed laptop. I kept typing 'Student User' for my user name and MatLab kept yelling at me for being the wrong user. Tried 'set username' and found that my ACTUAL user name was 'Administrator'. Tried that and it works!
• Jan 24, 2020  If you know the name and password of an admin account on your Mac, you can use that account to reset the password. Log in with the name and password of the other admin account. Choose System Preferences from the Apple menu, then click Users & Groups. Click, then enter the admin name and password again. Select your user name from the list of users.

First rename the home folder

1. Log out of the account you're renaming, then log in to a different administrator account. (If you don't have another administrator account, you can create one in Users & Groups preferences.)
   
2. Open the Users folder on the startup disk. It contains the home folder for each user. To get there, you can choose Go > Go to Folder from the menu bar, then enter /Users.
3. Rename the user's home folder without using any spaces in the new name. You'll be prompted to enter the administrator name and password that you used to log in. If you're using file sharing to share the home folder, you won't be able to rename it until you stop sharing the folder.

Then rename the account

While still logged out of the account you're renaming, follow these additional steps:

1. Choose Apple () menu > System Preferences, then click Users & Groups.
2. Click , then enter the administrator name and password that you used to log in.
3. From the list of users on the left, Control-click the user you're renaming, then choose Advanced Options.
4. Change the “Account name” field to match the new name of the home folder. It should have no spaces.
   
5. The account name also appears in the “Home directory” field, after /Users/. Change that account name to match the new name of the home folder.
6. If you want to change the full name associated with your account, update the ”Full name” field as well. It can be any name, and you can use either the full name or the account name to log in to your Mac or make changes that require your name and password.
7. Click OK, then restart your Mac.
8. Log in to the renamed account, then verify that your old files and folders are visible and the account is working as expected.

Choose an account for automatic login

1. Choose Apple menu  > System Preferences, then click Users & Groups.
2. Click the lock , then enter the account password.
   If you aren't logged in as an administrator, you're asked to enter an administrator name and password.
3. Click Login Options in the lower-left corner.
4. Choose an account from the “Automatic login” menu, then enter the password of that account.
   

Macos Asks For User Names

The account is now set up to log in automatically when your Mac starts up. You might still be asked to log in manually after logging out, switching back from another user account, or locking your screen.

If automatic login is unavailable

When manual login is required, the “Automatic login” menu is dimmed or doesn't show the account name. For example:

• If FileVault is turned on, manual login is required for all accounts. You can turn FileVault off.
• If an account uses an iCloud password to log in, manual login is required for that account. You might also see the message “A user with an encrypted home folder can't log in automatically.” When changing the account password, you can choose not to use the iCloud password.

Macos Asks For User Name Change

Log in after sleep or screen saver begins

You might still need to enter your password when your Mac wakes from sleep or stops using the screen saver. You can change this behavior:

Macos User Account

1. Choose Apple menu  > System Preferences, then click Security & Privacy.
2. In the General pane, deselect ”Require password after sleep or screen saver begins.” Or leave it selected, but choose a time interval from the pop-up menu: